(1B) The product $(a+b)(c+d)$
Practice
Expand and simplify.
*Write your answers with powers of $x$ in descending order. $\left(\square x^2 \pm \square x \pm \square\right)$
$\left(x+4\right)\left(x-4\right)$
$\left(x+9\right)\left(x+7\right)$
$\left(x+4\right)\left(9-x\right)$
$\left(x-9\right)\left(4-x\right)$
$\left(-9+x\right)\left(x+6\right)$
$\left(-3+x\right)\left(-x+3\right)$
$\left(7-x\right)\left(8-x\right)$
$\left(-4+x\right)\left(5+x\right)$
$\left(x-9\right)\left(2x-1\right)$
$\left(-8x+3\right)\left(x-7\right)$
$\left(2x+5\right)\left(-7+6x\right)$
$\left(-x+2\right)\left(7-4x\right)$
$\left(5-x\right)\left(2x-9\right)$
$\left(-6+7x\right)\left(6x+1\right)$
$\left(-1+5x\right)\left(-1+5x\right)$
$\left(4+5x\right)\left(-1+3x\right)$